You can take the config files and binary from any version and replace what is in the package. Just put everything in exactly the same place it is currently in for it to work. Because privoxy is not really compiled with any special locations, it is configured and the package uses one extra configuration file to do that (/etc/privoxy.cfg)

I used 3.0.3r2 because it was the newest that actually ran. But Dingetje has a 3.0.3 binary that could just replace the binary and might run better. You also as stated above completely change versions with an older version Because the package scripting does not care what version is installed.

If you are afraid that you might make a mistake. The chances are high that you will never learn anything.